Air flow control means for pulverizing mill



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- May 2.121.970 ASHDOWN 3,511,445

AIR-FLOW CONTROL MEANS FOR PULVERIZING MILL Filed April 5, 1968 2 Sheets-Sheet 2 3,511,445 AIR FLOW CONTROL MEANS FOR PULVERIZING MILL Ronald A. Ashdown, 2 Westway Gardens, Redhill, Surrey, England Filed Apr. 5, 1968, Ser. No. 719,139 Int. Cl. B02c 23/00 US. Cl. 241-61 ABSTRACT OF THE DISCLOSURE This invention relates to pulverizing mills of the type comprising a rotated horizontal table against which are forced a number of wheels or balls. A ring of nozzles through which air passes to entrain the pulverized materials surrounds the table, the nozzles of the ring being defined by a plurality of radial spacers, and the rate of lllOW of air through these nozzles is adjusted by wear blocks which fit over the radial spacers and adjust the size of nozzles.

BACKGROUND OF THE INVENTION These vertical spindle mills comprise a rotated horizontal table against which are forced a number of wheels or balls. The material to be pulverized, which may for example be coal, limestone or cement, is fed onto this table and is crushed by the wheels or balls. A stream of air is fed to the mill and this passes through a ring of nozzles arranged around the edge of the table. The pulverized material is entrained by the air passing through these nozzles and is taken to a classifier where oversized material is rejected and returned to the table.

A stationary nozzle ring is normally positioned around the horizontal table and in this ring are a set of evenly spaced openings which constitute the nozzles. It is, however, extremely difficult to calculate in advance the required sizes of these nozzles so as to get the desired rate of air flow. Also this required rate of flow depends upon the particular material which is being ground. Therefore, it has beeen the practice to design the ring so that the air flow through the nozzles will be too slow and then to adjust this air flow once the mill has been assembled by blocking off one or more of these nozzles. This has the disadvantage that the air flow around the table is no longer evenly distributed.

It has also been found that considerable wear of this ring takes place where the ring is exposed to the abrasive action of a flow of air carrying the pulverized material.

The invention has been made with these problems in mind.

According to the invention there is provided a vertical spindle pulverizing mill comprising a rotatable table against which are urged crushing members so that material fed to the table is crushed between it and the crushing members, as the table is rotated and a ring of nozzles surrounding the table through which streams of air can be passed to entrain the crushed material, the nozzles being defined between adjacent pairs of a number of wear blocks which are annularly spaced from one another around the outside of the table above an annular air supply duct, so that the choice of wear blocks of a particular size provides nozzles of a desired cross sectional area and a corresponding air flow rate through the nozzles.

According to one simple embodiment of the invention a nozzle ring having a plurality of radial spacers and the wear blocks are fitted to these spacers, the nozzles being defined between adjacent blocks and being of a size which is dependent upon the size of these blocks.

In this way, the air flow required through the nozzles Patent Claims 3,511,445 Patented May 12, 1970 can be adjusted very accurately and simple once the mill has been assembled by using blocks of the correct size and the adjusted air flow is evenly distributed around the table. Also if one or more of the blocks become worn during use they can be readily replaced by new blocks during routine maintenance, without the necessity of dismantling the mill to replace the whole nozzle ring.

A further advantage of the invention is that of standardisation. Thus, pulverizing mills for a variety of different materials can be designed to have similar nozzle rings and then these rings can be fitted with the correctly sized wear blocks to provide nozzles of the right size for use in pulverizing a particular material.

Preferably the wear blocks fit over the radial spacers and for this purpose they may have slots with dimensions corresponding to the dimensions of the radial spacers.

The wear blocks themselves can be cast from a cheap material such as cast iron. If, however, the material being pulverized is particularly abrasive, it may be desirable to make the blocks of a more wear resistant material.

DESCRIPTION OF THE DRAWINGS A vertical spindle pulverizing mill in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a general sectional elevation of the mill;

FIG. 2 is a plan detail of part of a nozzle ring;

FIG. 3 is a sectional detail of part of the nozzle ring;

FIG. 4 is a front elevation of a wear block to fit on the ring; and

FIG. 5 is a side elevation of a wear block.

DESCRIPTION OF THE PREFERRED EMBODIMENT The vertical spindle pulverizing mill 10 shown in FIG. 1 comprises rollers 12 which are pressed by means of a ring 14 against a grinding table 16 which is rotated by a drive 18. The material to be crushed is fed through an inlet duct 20 from whence it drops onto the table 16 and is crushed by the rollers 12.

Air is fed to the mill through an inlet conduit 22 and it passes to an annular chamber 24 below and around the edge of the table 16. The air passes from the chamber 24 through a nozzle ring 26 and it then picks-up the finely crushed material falling over the edge of the table 16. The air and entrained material pass upwardly through the mill to a classifier 28 where oversized material is rejected and returned to the table while the finely pulverized material and air leave the mill.

Previously the nozzle ring 26 has been cast in one piece so as to define a ring of nozzles of such a size that the rate of flow of air through them is as near as possible that which is necessary to entrain material of the desired fineness while entraining as small an amount as possible of material which is too large. This means that the nozzle ring has to be specially designed for each mill and also depends upon the material being ground. Also, to obtain final adjustment of the air flow some nozzles are blocked off, and so the air distribution becomes uneven. There is the further disadvantage that wearing of the ring takes place in use and as soon as one part of the ring becomes worn or damaged the whole ring must be replaced and the mill dismantled to enable this to be achieved.

According to the invention the ring 26 comprises a pair of coaxial end spaced ring members 28 and 30 between which extend radial spacers 32. The outer ring member 2-8 has a flange 34 by which the ring 26 is attached to the mill.

Once the ring 26 is in position in the mill, wear blocks 36 are fitted over the spacers 32, the blocks 36 having slots 38 to accommodate the spacers, and taped holes 40 into which eye bolts can be screwed to help in handling them. The positions of the blocks 36 are shown in dotted lines 42 in FIGURE 2 and between adjacent blocks nozzles 44 are defined.

It will be appreciated that the blocks 36 can be fitted to the ring 26 after the remainder of the mill has been assembled. Also by selecting blocks of the correct dimensions the opening of the nozzles 44 can be finely adjusted so as to give optimum results for each mill, while at the same time a standard ring 26 can be employed. Also since no nozzles are blocked-off the distribution of the air around the table is uniform.

Also if wearing or damage to any block occurs, all that is necessary is to stop the mill and replace that block without having to dismantle the mill. The blocks themselves are exposed to any wearing action which takes place and so the ring 26 is protected and is not likely to need replacement.

The material of the blocks 36 will depend upon the material being crushed. We have found that for the grinding of coal, the blocks can be of cast iron, although if desired the blocks or their surfaces may be of a harder wearing material.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

What is claimed is:

1. A vertical spindle pulverizing mill comprising a table (16), crushing members (12) urged against said table, means (18) for rotating said table, whereby material fed to said table is crushed between it and said crushing members (12) when the table is rotated, a ring of nozzles (44) surrounding said table, an annular air duct (24) in connection with said nozzles (44), means for supplying air to said duct (24), so that air passing through said nozzles entrains material crushed on said table (16), and a plurality of wear blocks (36) annularly spaced around said table (116) above said duct (24), the nozzles (44) being defined between adjacent pairs of these blocks (36), whereby choice of wear blocks of a particular size provides nozzles of a desired cross sectional area and a corresponding air flow rate through said nozzles.

2. A mill according to claim 1 further comprising a pair of radially spaced concentric ring members (28, 30) surrounding said table (16), and radial spacers (32) extending between said ring members (28, 30) said wear blocks (36) being arranged over Said radial spacers (32).

3. A mill according to claim 2 in which said wear blocks (36) have recesses (38) corresponding to said size and shape of said spacers (32), the blocks being positioned over the spacers so that said spacers are received in said recesses (38).

4. In a vertical spindle pulverizing mill, the provision of a nozzlering comprising an inner ring (30), an outer ring (28) coaxial with and spaced from said inner ring, and a plurality of radial spacers (32) extended between said inner and outer rings, and the provision of a plurality of wear blocks (36) fitting over said radial spacers (32), nozzles (44) being defined between adjacent blocks and being of a size which is dependent upon the size of those blocks.

5. A vertical spindle pulverizing mill comprising a housing, a circular table rotatably mounted within said housing, means for rotating said table, a plurality of crushing members, resilient means urging said crushing members against said table, feed means for supplying material to be crushed to said table, a plurality of nozzles positioned around said table, an annular air supply duct under said nozzles, means for supplying air to said duct, classifier means positioned above said table for receiving air from said nozzles and entrained crushed material from said table, said classifier means returning oversized material to said table, and outlet means from said classifier means for air and entrained crushed material, said nozzles being defined between adjacent pairs of a plurality of removable and replaceable wear blocks annularly spaced around said table.

References Cited UNITED STATES PATENTS 2,206,145 7/1940 Wood 241-61 2,545,254 3/1951 Bice .241-61 3,366,338 1/1968 Barton 24152 GERALD A. DOST, Primary Examiner US. Cl. X.R. 24l-301 

